All of the commonly practiced processes for fabricating three-dimensional objects have disadvantages. For example, the mechanical removal of material to form such objects involves much energy, time and processing; the chemical machining to form such objects has depth limitations and the incapability of making complex shapes; and the thermal molding requires expensive molds, is very inflexible and takes much time and energy.
Several methods and apparatus have been developed for the production of three-dimensional objects by irradiation of photopolymers that cross-link and solidify upon irradiation.
Forming three-dimensional objects by solidifying each point individually can be accomplished by scanning the whole volume of the object point by point with two intersecting beams, as described, for example, in U.S. Pat. Nos. 4,041,476 and 4,288,861. However, such methods are very complex and expensive. The forming of three-dimensional objects by buildingup succesive very thin laminae of the solidified photopolymer is described in U.S. Pat. No. 4,575,330. The method involves many production steps due to the large number of laminae required, especially for objects with inclined or curved walls. Since an open surface is irradiated, there is shrinkage and resulting distortion. There also are limitations on feasible geometries. In my U.S. patent application Ser. No. 20,764 filed on Mar. 2, 1987 now U.S. Pat. No. 4,752,498 is described fabrication by building up succesive layers. Each layer is formed by irradiation through a rigid radiation transmittent material which is in contact with the uncured photopolymer to minimize shrinkage distortion, and which leaves the irradiated surface capable of further cross-linking so that a subsequently formed layer adheres thereto. The amount of irradiation is modulated across the irradiated surface to vary depth of solidification. This method also features geometrical limitations due to the forming by whole layers.
Three-dimensional objects of various geometries are widely used everywhere in final products, prototypes and models. A large number of such objects could be made of photopolymers by photosolidification if there were a suitable apparatus and method of producing these objects which resulted in dramatic reductions in cost and time and improvements in accuracy and performance.